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Studying AGB stars with high spectral resolution infrared observations

AuthorsFonfría, José Pablo ; Cernicharo, José ; Richter, M. J.; Lacy, J. H.; Hinkle, K. H.; Montiel, E. J.; Santander-García, M.; DeWitt, C. N.; Greathouse, T. K.
Issue Date27-Aug-2019
CitationA Star Has Evolved (2019)
AbstractDuring the last decades, much work has been done to understand the physical and chemical evolution of AGB stars. Most of this knowledge has been derived from the analysis of single-dish or interferometer millimeter observations. With them, we have been able to establish the basis of the chemistry in circumstellar envelopes and to find out the mechanisms involved in the matter ejection process, that relies on the stellar pulsation and the dust grains formed by the depletion of gas-phase refractory molecules. However, millimeter observations are unable to trace the emission of molecules without a permanent dipole moment, such as a number of organic species (e.g., C2H2, C4H2, C6H2 or benzene) that could be involved in the growth of dust grains in C-rich stars, or oxygen bearing molecules such as CO2 in O-rich stars. The analysis of the molecular excitation in the inner layers of the envelopes, tightly related to the gas kinetic temperature and the infrared radiation field produced by the central cool stars and the dust around them, is hampered by the usually low line density of the parent molecules in the millimeter range. It is uncommon to observe more than a few lines of light molecules simultaneously and heavier molecules, with more complex spectra, are less abundant and they are affected by the gas chemistry, making them bad tracers of the gas close to the stars. High spectral resolution single-dish infrared observations help us to solve some of these problems, complementing and verifying the results derived from millimeter observations. We aim to present a summary of the application of this observing technique to the study of the circumstellar envelopes of AGB stars. We will focus on our work carried out during the last 15 years, which have been based on the analysis and modeling of mid- and near-infrared spectra acquired with the spectrographs TEXES, EXES and iSHELL, mounted on the IRTF and SOFIA.
DescriptionA conference in the honor of Hans Olofsson, Smögen, Sweden, August 27 - 29, 2019
Appears in Collections:(CFMAC-IFF) Comunicaciones congresos
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